EP0001427A1 - 2,6-Dichloro-3'-fluoro-4-trifluoromethyl-6'-nitrodiphenyl ether, a process for its preparation and its application as a defoliation agent for cotton - Google Patents

Abstract

1. 2,6-Dichloro-3'-fluoro-4-trifluoromethyl-6'- -nitrodiphenyl ether of the formula see diagramm : EP0001427,P6,F4

Description

The present invention relates to the new 2,6-dichloro-3'-fluoro-4-trifluoromethyl-6'-nitrodiphenyl ether, a process for its preparation and its use as a defoliant in cotton.

It has already become known that S, S, S-tributylphosphorothrithioate can be used as a defoliation agent in cotton (cf. US Pat. Nos. 2,841,486 and 2,965,467). However, the effect of this substance is not always completely satisfactory at low doses, especially not because the re-sprouting of leaves in the cotton plants is not prevented. The compound is also unpleasant to handle because of its intense smell.

Gegenstand der Erfindung ist auch ein Verfahren zur Herstellung des 2,6-Dichlor-3'-fluor-4-trifluormethyl-6'-nitro-diphenyläthers der Formel (I) durch Umsetzung von 2,6-Dichlor-4-trifluormethylphenol der Formel

mit 2,4-Difluor-nitrobenzol der Formel

unter wasserfreien Bedingungen in Gegenwart eines Säureakzeptors sowie in Gegenwart eines Verdünnungsmittels.This invention relates to the new 2,6-dichloro-3'-fluoro-4-trifluoromethyl-6'-nitrodiphenyl ether of the formula

The invention also relates to a process for the preparation of 2,6-dichloro-3'-fluoro-4-trifluoromethyl-6'-nitro-diphenyl ether of the formula (I) by reacting 2,6-dichloro-4-trifluoromethylphenol of the formula

with 2,4-difluoro-nitrobenzene of the formula

under anhydrous conditions in the presence of an acid acceptor and in the presence of a diluent.

The invention furthermore relates to the use of 2,6-dichloro-3'-fluoro-4-trifluoromethyl-6'-nitro-diphenyl ether of the formula (I) for defoliation of cotton plants, for preventing the re-shoot in cotton Plants for drying the leaves of cotton plants and for inhibiting the development of insects and arachnids.

Surprisingly, the 2,6-dichloro-3'-fluoro-4-trifluoromethyl-6'-nitro-diphenyl ether is more suitable for defoliation of cotton plants than the S, S, S-tributyl-phosphorotrithioate known from the prior art, which is a recognized well-effective substance of the same type of action. The connection according to the invention thus represents a valuable addition to the technology.

The preparation of 2,6-dichloro-3'-fluoro-4-trifluoromethyl-6'-nitro-diphenyl ether by reacting 2,6-dichloro-4-trifluoromethylphenol with 2,4-difluoro-nitrobenzene in the presence of potassium hydroxide can be illustrated by the following formula scheme:

The compounds of the formulas (II) and (III) required as starting materials in the preparation of the 2,6-dichloro-3'-fluoro-4-trifluoromethyl-6'-nitro-diphenyl ether are already known (cf. Chem. Ind. ( London) 1962, No. 29, 1328-1329 and DT-OS 2.407.148).

When carrying out the process according to the invention, customary acid binders can act as acid acceptors. These preferably include alkali hydroxides, such as potassium hydroxide and sodium hydroxide.

Inert, high-boiling organic solvents can be used as diluents in the reaction according to the invention. These preferably include dimethyl sulfoxide and tetramethylene sulfone.

The reaction temperatures in the ^* reaction according to the invention can be varied within a substantial range. In general, temperatures between 80 ° C and 140 ° C, preferably between 100 ° C and 120 ° C.

Anhydrous conditions can be achieved in the process according to the invention in such a way that a phenolate is prepared from the 2,6-dichloro-4-trifluoromethylphenol and an acid acceptor and the latter is then reacted with 2,4-difluoro-nitrobenzene. If an alkali metal hydroxide is used as the acid acceptor, the water formed during the reaction is expediently removed with the aid of organic solvents, such as e.g. Toluene or benzene, azeotropically distilled off.

When carrying out the process according to the invention, 1 mol of 2,4-difluoro-nitrobenzene and an equivalent amount of acid binder are employed per mol of 2,6-dichloro-4-trifluoromethylphenol.

The reaction product is isolated by customary methods. In general, the procedure is such that, after the reaction has ended, the solvent is first distilled off, water is added to the remaining residue, then extracted with an organic solvent, such as methylene chloride, and the organic phase is then dried and concentrated. The resulting residue contains not only the 2,6-dichloro-3'-fluoro-4-trifluoromethyl-6'-nitro-diphenyl ether but also the 2,6-dichloro-3'-fluoro-4-trifluoromethyl-4'-nitro- diphenyl ether. The 2,6-dichloro-3'-fluoro-4-trifluoromethyl-6'-nitro-diphenyl ether can be obtained by repeatedly recrystallizing the crude product isolate it in a suitable organic solvent, e.g. hexane.

The active ingredient according to the invention induces the dropping of leaves in plants and can be used in particular as a defoliant in cotton plants, to prevent re-sprouting and to dry out the leaves in cotton plants.

Furthermore, the active ingredient according to the invention is suitable as an inhibitor of the development of insects and arachnids for controlling pests.

With good plant tolerance and favorable warm-blood toxicity, the active ingredient is suitable for controlling animal pests, in particular insects and arachnids, which occur in agriculture, in forests, in the protection of stored goods and materials, and in the hygiene sector. It is effective against normally sensitive and resistant species as well as against all or individual stages of development. The pests mentioned above include:

From the order of the Isopoda z. B. Oniscus asellus, Armadillidium vulgare, Porcellio scaber.
From the order of the Diplopoda z. B. Blaniulus guttulatus.
From the order of the Chilopoda z. B. Geophilus carpophagus, Scutigera spec.
From the order of the Symphyla z. B. Scutigerella immaculata.
From the order of the Thysanura z. B. Lepisma saccharina.
From the order of the Collembola z. B. Onychiurus armatus.
From the order of the Orthoptera z. B. Blatta orientalis, Periplaneta americana, Leucophaea muderae, Blattella germanica, Acheta domesticus, Gryllotalpa spp., Locusta migratoria migratorioides, Melanoplus differentialis, Schistocerca gregaria.
From the order of the Dermaptera z. B. Auricular Forficula.
From the order of the Isoptera z. B. Reticulitermes spp ..
From the order of the Anoplura z. B. Phylloxera vastatrix, Pemphigus spp., Pediculus humanus corporis, Haematopinus spp., Linognathus spp.
From the order of the Mallophaga, for example Trichodectes spp., Damalinea spp.
From the order of the Thysanoptera, for example Hercinothrips femoralis, Thrips tabaci.
From the order of the Heteroptera, for example Eurygaster sp ^p ., Dysdercus intermedius, Piesma auadrata, Cimex lectularius, Rhodnius prolixus, Triatoma spp.
From the order of the Homoptera, for example, Aleurodes brassicae, Bemisia tabaci, Trialeurodes vaporariorum, Aphis gossypii, Brevicoryne brassicae, Cryptomyzus ribis, Doralis fabae, Doralis pomi, Eriosoma lanigerum, Hyalopterus arundinis, Macrosiphum avenae, Phusoponosum., Myzus sppas spp., Euscelis bilobatus, Nephotettix cincticeps, Lecanium corni, Saissetia oleae, Laodelphax striatellus, Nilaparvata lugens, Aonidiella aurantii, Aspidiotus hederae, Pseudococcus spp., Psylla spp ..
From the order of the Lepidoptera z. B. Pectinophora gossypiella, Bupalus piniarius, Cheimatobia brumata, Lithocolletis blancardella, Hyponomeuta padella, Plutella maculipennis, Malacosoma neustria, Euproctis chrysorrhoea, Lymantria spp., Bucculatrix thurberiisisppa, Fpp , Heliothis spp., Laphygma exigua, Mamestra brassicae, Panolis flammea, Prodenia litura, Spodoptera spp., Trichoplusia ni, Carpocapsa pomonella, Pieris spp., Chilo spp., Pyrausta nubilalis, Ephestia kuehniella, Caulioacoua pellella, Galleria capuaella Choristoneura fumiferana, Clysia ambiguella, Homona magnanima, Tortrix viridana.
From the order of the Coleoptera z. B. Anobium punctatum, Rhizopertha dominica, Bruchidius obtectus, Acanthoscelides obtectus, Hylotrupes bajulus, Agelastica alni, Leptinotarsa decemlineata, Phaedon cochleariae, Diabrotica sp ^p. , Psylliodes chrysocephala, Epilachna varivestis, Atomaria s ^p r., Oryzaephilus surinamensis, Anthonomus spp., Sitophilus spp., Otiorrhynchus sulcatus, Cosmopolites sordidus, Ceuthorrhynchus assimilis, Hypera postpp. Spp., Att., Ant ., Lyctus spp., Meligethes aeneus, Ptinus spp., Niptus hololeucus, Gibbium psylloides, Tribolium spp., Tenebrio molitor, Agriotes spp., Conoderus spp., Melolontha melolontha, Amphimallon solstitialis, Costelytra zealandica.
From the order of the Hymenoptera z. B. Diprion spp., Hoplocampa spp., Lasius spp., Monomorium pharaonis, Vespa spp.
From the order of the Diptera, for example Aedes s ^p p., Anopheles s ^p p., Culex spp., Drosophila melanogaster, Musca spp., Fannia spp., Calliphora erythrocephala, Lucilia spp., Chrysomyia s ^p p., Cuterebra spp., Gastrophilus s ^p p., Hyppobosca spp., Stomoxys spp., Oestrus spp., Hypoderma spp., Tabanus spp., Tannia spp., Bibio hortulanus, Oscinella frit, Phorbia s ^p p., Pegomyia hyoscyami, Ceratitis capitata, Dacus oleae , Tipula paludosa.
From the order of the Siphonantera, for example Xenopsylla cheopis, Ceratophyllus spp ..
From the order of the Arachnida, for example Scorpio maurus, Latrodectus mactans.
From the order of the Acarina, for example Acarus siro, Argas spp., Ornithodoros spp., Dermanyssus gallinae, Eriophyes ribis, Phyllocoptruta oleivora, Boophilus spp., Rhipicephalus spp., Amblyomma spp., Hyalomma spp., Ixodes spp., Psoroptes, Chorioptes spp., Sarcoptes spp., Tarsonemus spp., Bryobia praetiosa, Panonychus spp., Tetranychus spo ..

In low concentrations, the active ingredient according to the invention shows an development-inhibiting activity on individual or all stages of development of insects.

The active ingredient can be converted into the usual formulations, such as solutions, emulsions, wettable powders, suspensions, powders, dusts, foams, pastes, soluble powders, granules, aerosols, suspension emulsion concentrates, seed powders, active ingredient-impregnated natural and synthetic substances, very fine encapsulations in polymeric substances and in coating compositions for seeds, also in formulations with fuel sets, such as smoking cartridges, cans, spirals, etc. as well as ULV cold and warm fog formulations.

• gebrochene und fraktionierte natürliche Gesteine wie Calcit, Marmor, Bims, Sepiolith, Dolomit sowie synthetische Granulate aus anorganischen und organischen Mehlen sowie Granulate aus organischem Material wie Sägemehle, Kokosnußschalen, Maiskolben und Tabakstengel; als Emulgier-und/oder schaumerzeugende Mittel: nichtionogene und anionische Emulgatoren, wie Polyoxyäthylen-Fettsäure-Ester, Polyoxyäthylen-Fettalkohol-Äther, z.B. Alkylaryl-polyglykol-äther, Alkylsulfonate, Alkylsulfate, Arylsulfonate sowie Eiweißhydrolysate; als Dispergiermittel: z.B. Lignin-Sulfitablaugen und Methylcellulose.

These formulations are prepared in a known manner, for example by mixing the active ingredients with extenders, that is to say liquid solvents, pressurized liquefied gases and / or solid carriers, optionally using surface-active agents, that is to say emulsifiers and / or dispersants and / or foam-generating agents. If water is used as an extender, organic solvents can, for example, also be used as auxiliary solvents. The following are essentially suitable as liquid solvents: aromatics, such as xylene, toluene, or alkylnaphthalenes, chlorinated aromatics or chlorinated aliphatic hydrocarbons, such as chlorobenzenes, chloroethylene or methylene chloride, aliphatic hydrocarbons, such as cyclohexane or paraffins, for example petroleum fractions, alcohols, such as butanol or glycol and their ethers and esters, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone or cyclohexanone, strongly polar solvents such as dimethylformamide and dimethyl sulfoxide, and water; Liquefied gaseous extenders or carriers mean liquids which are gaseous at normal temperature and under normal pressure, for example aerosol propellant such as halogenated carbon substances such as butane, propane, nitrogen and carbon dioxide; as solid carriers: natural rock flour, such as kaolin, clay, talc, chalk, quartz, attapulgite, montmorillonite or diatomaceous earth and synthetic rock powder, such as highly disperse silica, aluminum oxide and silicates; as solid carriers for granules:

• broken and fractionated natural rocks such as calcite, marble, pumice, sepiolite, dolomite and synthetic granules from inorganic and organic flours as well as granules from organic material such as sawdust, coconut shells, corn cobs and tobacco stems; as emulsifiers and / or foam-generating agents: nonionic and anionic emulsifiers, such as polyoxyethylene fatty acid esters, polyoxyethylene fatty alcohol ethers, for example alkylaryl polyglycol ethers, alkyl sulfonates, alkyl sulfates, aryl sulfonates and protein hydrolyzates; as dispersing agents: eg lignin sulfite liquor and methyl cellulose.

Adhesives such as carboxymethyl cellulose and natural and synthetic polymers in the form of powders, granules or latices, such as gum arabic, polyvinyl alcohol and polyvinyl acetate, can be used in the formulations.

Dyes such as inorganic pigments, e.g. Iron oxide, titanium oxide, ferrocyan blue and organic dyes such as alizarin, azo metal phthalocyanine dyes and trace nutrients such as salts of iron, manganese, boron, copper, cobalt, molybdenum and zinc can be used.

The formulations generally contain between 0.1 and 95 percent by weight of active compound, preferably between 0.5 and 90%.

The active ingredient according to the invention can be present in the formulations in a mixture with other known active ingredients, such as fungicides, insecticides, acaricides and herbicides.

The active ingredient can be used as such in the form of its formulations or the use forms prepared therefrom, such as ready-to-use solutions, emulsifiable concentrates, emulsions, foams, suspensions, wettable powders, soluble powders, dusts. They are used in the usual way, e.g. by pouring, spraying, atomizing, dusting, foaming, gassing, etc. It is also possible to apply the active ingredient by the ultra-low-volume process.

When the active ingredient is used to defoliate cotton plants or to prevent re-sprouting or to dry out the leaves in cotton plants, the active ingredient concentrations can be increased

Range can be varied. In general, concentrations from 0.00005 to 2%, preferably from 0.0001 to 0.2%, are used. Furthermore, 0.01 to 50 kg, preferably 0.05 to 10 kg, of active ingredient are generally used per hectare of soil.

For the application time of the active ingredient in cotton, the application should be carried out in a preferred period, the exact delimitation of which depends on the climatic and vegetative conditions.

In one application of the active ingredient for inhibiting the development of insects and arachnids, the active ingredient content of the prepared from the commercially available formulations can _dun applications g _sformen vary within wide ranges. The active ingredient The concentration of the use forms can be from 0.0000001 to 100% by weight of active compound, preferably between 0.01 and 10% by weight.

The application takes place in a customary manner adapted to the application forms.

When used against hygiene pests and pests of stored products, the active ingredient is distinguished by an excellent residual action on wood and clay and by a good stability to alkali on limed substrates.

The following example shows the use of the substance according to the invention as an agent for defoliation of cotton plants and for preventing re-sprouting in cotton plants.

Example A: Defoliation, re-expansion and desiccation in cotton

Solvent: 10 parts by weight of dimethylformamide, 2 parts by weight of polyoxyethylene sorbitan monolaurate

To produce a suitable preparation of active compound, 1 part by weight of active compound is mixed with the stated amounts of solvent and emulsifier and the mixture is made up to the desired concentration with water.

Cotton plants are grown in plastic pots of 1 1 content until the 8th leaf unfolds in the greenhouse. The plants are then sprayed with the active compound preparations until the spray liquor drips off. After a further 8 days, the leaf fall induced by the preparations and the re-emergence are rated.

• 1) eine Wirkstoff-freie Formulierung
• 2) das als Baumwoll-Entblätterungsmittel bekannte S,S,S-Tributyl-phosphortrithioat
• 3) der erfindungsgemäße Wirkstoff 2,6-Dichlor-3'-fluor-4-trifluormethyl-6'-nitro-diphenyläther.

The following are tested side by side:

• 1) an active ingredient-free formulation
• 2) the S, S, S-tributyl-phosphorus trithioate known as cotton defoliants
• 3) the active ingredient 2,6-dichloro-3'-fluoro-4-trifluoromethyl-6'-nitro-diphenyl ether.

The active ingredients are used in concentrations of 0.2 and C, 05%.

In both cases, the active ingredient according to the invention is more suitable for defoliation of the cotton plants than the S, S, S-tributylphosphorothrithioate. Furthermore, the active ingredient according to the invention prevents the re-expulsion of leaves.

If the leaves do not fall off under the influence of the active ingredient according to the invention, they dry out completely (desiccant effect), a desired effect which is not achieved to this extent by S, S, S-tributyl-phosphorotithioate.

The examples below show the use of the active compound according to the invention for inhibiting the development of insects.

When carrying out the test, the morphological changes, such as half pupated animals, incompletely hatched larvae or caterpillars, defective wings, pupal cuticles in adults, etc., are assessed as malformations during the entire development of the test animals.

The sum of the morphological malformations, together with the animals killed during the molting process or the metamorphosis, is determined as a percentage of the total number of experimental animals.

Example B Developmental inhibitory effect / feeding test

Zur Herstellung einer zweckmäßigen Wirkstoffzubereitung vermischt man 2 Gew.-Teile Wirkstoff mit der angegebenen Menge Lösungsmittel, Emulgator und soviel Wasser, daß eine 1%ige Mischung entsteht, die mit Wasser auf die gewünschte Konzentration verdünnt wird.

To produce a suitable preparation of active compound, 2 parts by weight of active compound are mixed with the stated amount of solvent, emulsifier and enough water to form a 1% mixture which is diluted with water to the desired concentration.

The test animals are fed leaves of the fodder plants, which are coated with a uniform spray coating of the active compound mixture in such a way that the selected active compound concentration per unit area on the leaves is reached, until the development of the Imago.

As a control, only leaves coated with solvent and emulsifier / water mixture of the selected concentration are fed.

In this test, the compound according to the invention shows a superior action compared to the prior art.

Example C Developmental inhibitory effect / Laphygma test

Zur Herstellung einer zweckmäßigen Wirkstoffzubereitung vermischt man 2 Gew.-Teile Wirkstoff mit der angegebenen Menge Lösungsmittel, Emulgator und soviel Wasser, daß eine 1 %ige Mischung entsteht, die mit Wasser auf die gewünschte Konzentration verdünnt wird.

To produce a suitable preparation of active compound, 2 parts by weight of active compound are mixed with the stated amount of solvent, emulsifier and enough water to form a 1% mixture which is diluted with water to the desired concentration.

One test animal each is placed on a feed disc moistened with 1.5 ml of active ingredient solution of the specified concentration and observed until the Imago hatches.

As a control, a test animal is placed on a feed disc moistened with 1.5 ml of solvent and emulsifier of the appropriate concentration and observed until the Imago hatches.

In this test, the compound according to the invention shows a superior action compared to the prior art.

Example D Development-inhibiting effect

Zur Herstellung einer zweckmäßigen Wirkstoffzubereitung vermischt man 2 Gew.-Teile Wirkstoff mit der angegebenen Menge Lösungsmittel, Emulgator und soviel Wasser, daß eine 100 ppmhaltige Mischung entsteht, die mit Wasser auf die gewünschte Konzentration verdünnt wird.

To prepare a suitable preparation of active compound, 2 parts by weight of active compound are mixed with the stated amount of solvent, emulsifier and enough water to form a mixture containing 100 ppm, which is diluted with water to the desired concentration.

The test animals are used in 90 ml of these active ingredient solutions and are observed until the Imago hatches. As a control, test animals are placed in a solvent and emulsifier / water mixture of the specified concentration and observed until the imago hatches.

In this test, the compound according to the invention shows a superior action compared to the prior art.

Manufacturing example

23,1 g (0,1 Mol) 2,6-Dichlor-4-trifluormethylphenol werden in 70 ml Tetramethylensulfon gelöst und mit 5,6 g (0,1 Mol) Kaliumhydroxid versetzt. Es werden 50 ml Toluol zugegeben, dann wird 2 Stunden lang das entstandene Reaktionswasser azeotrop abdestilliert. Anschließend wird das überschüssige Toluol abdestilliert. Zu der verbleibenden Mischung werden 15,9 g (0,1 Mol) 2,4-Difluor-nitrobenzol zugetropft. Nach beendeter Zugabe wird das Reaktionsgemisch 10 Stunden bei 120°C gerührt. Danach wird das Tetramethylensulfon unter vermindertem Druck (10 Torr) bei einer Badtemperatur von 160⁰C abdestilliert. Der Rückstand wird mit Wasser versetzt und mit Methylenchlorid extrahiert. Die organische Phase wird abgetrennt, über Natriumsulfat getrocknet und durch Kochen mit Aktivkohle geklärt. Nach dem Einengen der Lösung verbleiben 24 g (65 % der Theorie) eines hellgelben öles, das gemäß Gaschromatogramm zu 20 % aus dem 2,6-Dichlor-3'-fluor-4-trifluormethyl-4'-nitrodiphenyl- äther und zu 80 % aus dem 2,6-Dichlor-3'-fluor-4-trifluormethyl-6'-nitro-diphenyläther besteht. Durch mehrfaches Umkristallisieren dieses Produktes aus n-Hexan wird der 2,6-Dichlor-3'-fluor-4-trifluormethyl-6'-nitro-diphenyl- äther rein isoliert. Die Substanz weist einen Schmelzpunkt von 91°C auf.

23.1 g (0.1 mol) of 2,6-dichloro-4-trifluoromethylphenol are dissolved in 70 ml of tetramethylene sulfone, and 5.6 g (0.1 mol) of potassium hydroxide are added. 50 ml of toluene are added, then the water of reaction formed is distilled off azeotropically for 2 hours. The excess toluene is then distilled off. 15.9 g (0.1 mol) of 2,4-difluoro-nitrobenzene are added dropwise to the remaining mixture. After the addition has ended, the reaction mixture is stirred at 120 ° C. for 10 hours. Thereafter, the tetramethylene (10 Torr) was distilled off under reduced pressure at a bath temperature of 160 ⁰ C. The residue is mixed with water and extracted with methylene chloride. The organic phase is separated off, dried over sodium sulfate and clarified by boiling with activated carbon. After concentrating the solution, 24 g (65% of theory) of a light yellow oil remain, which according to the gas chromatogram consists of 20% of the 2,6-dichloro-3'-fluoro-4-trifluoromethyl-4'-nitrodiphenyl ether and 80% % consists of the 2,6-dichloro-3'-fluoro-4-trifluoromethyl-6'-nitro-diphenyl ether. By repeatedly recrystallizing this product from n-hexane, the 2,6-dichloro-3'-fluoro-4-trifluoromethyl-6'-nitro-diphenyl ether is isolated in pure form. The substance has a melting point of 91 ° C.

Claims (6)

1. 2,6-dichloro-S'-fluoro-4-trifluoromethyl-6'-nitro-diphenyl ether of the formula

2. Process for the preparation of 2,6-dichloro-3'-fluoro-4-trifluoromethyl-6'-nitro-diphenyl ether, characterized in that 2,6-dichloro-4-trifluoromethylphenol of the formula

with 2,4-difluoro-nitrobenzene of the formula

under anhydrous conditions in the presence of an acid acceptor and in the presence of a diluent. 3. Means for defoliation of cotton plants, for preventing the re-sprouting of cotton plants for desiccating the leaves of cotton plants and for inhibiting the development of insects and arachnids, characterized by a content of 2,6-dichloro-3'-fluorine 4-trifluoromethyl-6'-nitrodiphenyl ether according to claim 1. 4. A process for defoliation of cotton plants, for preventing the re-emergence of cotton plants for desiccation of the leaves of cotton plants and for inhibiting the development of insects and arachnids, characterized in that 2,6-dichloro-3'-fluoro-4-trifluoromethyl- 6'-nitrodiphenyl ether according to claim 1 can act on the cotton plants or their habitat or on insects or arachnids or their habitat. 5. Use of 2,6-dichloro-3'-fluoro-4-trifluoromethyl-6'-nitro-diphenyl ether according to claim 1 for defoliation of cotton plants, for preventing the re-emergence of cotton plants for desiccation of the leaves of cotton plants and for inhibition the development of insects and arachnids. 6. A process for the preparation of an agent for defoliation of cotton plants, for preventing the re-emergence of cotton plants for desiccation of the leaves of cotton plants and for inhibiting the development of insects and arachnids, characterized in that 2,6-dichloro-3'-fluorine 4-trifluoromethyl-6'-nitro-diphenyl ether according to claim 1 mixed with extenders and / or surface-active agents.